If the programmers used a delayed require, those files won't show up. Furthermore, this doesn't show all possible files that get opened, just those that those up in %INC. Most systems have a way to trace system calls. You can use this to find the real answer. First, get a baseline with no modules loaded.

This is free software; you can redistribute it and/or modify it under the terms of either: (a) the GNU General Public License as published by the Free Software Foundation; either version 1, or (at your option) any later version, or (b) the Perl "Artistic License". (This is the Perl 5 licensing scheme.)

Please note this is a change from the original pmtools-1.00 (still available on CPAN), as pmtools-1.00 were licensed only under the Perl "Artistic License".